1. Field of Invention
The present invention relates to a semiconductor fabricating method. More particularly, the present invention relates to a method of forming a capacitor.
2. Description of Related Art
Dynamic Random Access Memory (DRAM) devices are used in wide range of electronics applications. DRAMs are designed mainly for the purpose of storing data. The operations on a memory device includes reading the data stored in the device, writing (or storing) data in the device, and refreshing the data periodically.
A capacitor being charged/discharged to determine a logic 1 or a logic 0 is incorporated in a DRAM cell. Due to the increasing number of semiconductor elements incorporated in integrated circuits, the size of DRAM cell is decreased. As the size of DRAM memory cell is decreased, the effective area available for forming capacitors decreases. As a consequence, the capacitors are formed with a shrunk surface area, that is, a contact area with a decreased capacitance. As the capacitance is reduced, the capacity of a datum stored in a DRAM cell is decreased.
FIG. 1 is a cross-sectional view of a portion of semiconductor device showing a conventional hemi-spherical grain capacitor.
In FIG. 1, a semiconductor substrate having a source/drain region 104 is provided. An isolation layer 106 is formed on the semiconductor substrate 100. A via opening 110 is formed in the isolation layer 106 to expose the source/drain region 104. A crown-shape bottom storage node 108 is formed over on the isolation layer 106 to fill the via opening 110. A hemi-spherical grain structure is formed only on the bottom inner side wall of the bottom storage node 108. With the formation of the hemi-spherical grain structure, the effective contact area of the bottom storage node 108 is increased. With an increased effective contact area, the capacitance of capacitor is increased.
In the conventional capacitor, the hemi-spherical grain structure 110 is not formed on the inner surfaces of the bottom storage node 108. Thus, the increase of the effective contact area is limited. As a consequence, the increase of capacitance is limited as well.